A known type of driver circuit for LEDs is a tapped linear driver. In a tapped linear driver (TLD) structure, LEDs are typically arranged in series and supplied with a varying operating voltage, such as a rectified mains voltage. Control assemblies, such as switches or current sources are connected to the taps, i.e. the interconnection points in the series connection. By suitable control, groups of the LED elements are operated depending on the momentarily available supply voltage.
WO 2010/027254 A1 describes an LED assembly comprising a serial connection of two or more LED units, each LED unit comprising one or more LEDs. Each LED unit is provided with a controllable switch for short-circuiting the LED unit. A converter, which may be a buck converter or boost converter, provides power to the LED units by converting an input power source to an appropriate current source for the LEDs. A control unit receives a signal representing a voltage level of the supply voltage and controls the switches in accordance with the signal.